Metal‐Organic Framework Thin Films Grown on Functionalized Graphene as Solid‐State Ion‐Gated FETs

Abstract

The unique properties of 2D‐materials like graphene are exploited in various electronic devices. In sensor applications, graphene shows a very high sensitivity, but only a low specificity. This shortcoming can be mastered by using heterostructures, where graphene is combined with materials exhibiting high analyte selectivities. Herein, this study demonstrates the precise deposition of nanoporous metal‐organic frameworks (MOFs) on graphene, yielding bilayers with excellent specificity while the sensitivity remains large. The key for the successful layer‐by‐layer deposition of the MOF films (SURMOFs) is the use of planar polyaromatic anchors. Then, the MOF pores are loaded with ionic liquid (IL). For functioning sensor devices, the IL@MOF films are grown on graphene field‐effect transistors (GFETs). Adding a top‐gate electrode yields an ion‐gated GFET. Analysis of the transistor characteristics reveals a clear Dirac point at low gate voltages, good on‐off ratios, and decent charge mobilities and densities in the graphene channel. The GFET‐sensor reveals a strong and selective response. Compared to other ion‐gated‐FET devices, the IL@MOF material is relatively hard, allowing the manufacturing of ultrathin devices. The new MOF‐anchoring strategy offers a novel approach generally applicable for the functionalization of 2D‐materials, where MOF/2D‐material hetero‐bilayers carry a huge potential for a wide variety of applications.